Chemically incompatible components

Safety aspects are considered in two phases (Fig. 11). In the rule based synthesis some safety related rules are applied in process concept selections. These include rules such as separate corrosive or hazardous components first or avoid using chemically incompatible substances in the same process. ... 

Seven of nine respondents use chemical interaction matrices to identify potential chemical incompatibilities. Most use a binary matrix (i.e., the mixing of only two chemical components at a time). Respondents indicated that literature or expert opinion are important sources of data for the matrix. 

Chemical incompatibility with fuel system components... 

In general the diffusion of a solute like Xe is not driven by the concentration gradients but by the chemical potential. In polymer blends with incompatible components, as we investigate here, in the equilibrium situation it may occur that different domains have different concentrations of Xe. Then the usual Fick laws do not hold. 

One of the simplest solutions to the problem of chemical incompatibility between oligonucleotides and peptides is to avoid the issue by preparing both components separately using peptide and oligonucleotide standard methodologies followed by linking both compounds together. Prior to the... 

If two polymers are mixed, the most frequent result is a system that exhibits complete phase separation due to the repulsive interaction between the components (i.e., the chemical incompatibility between the polymers). A necessary condition for miscibility to occur is that AG must be negative (AG < 0). This is a necessary requirement, but not a sufficient one, as the following expression must also be satisfied in order to obtain a stable one-phase system. The expression that describes the criteria for phase stability of binary mixtures of composition tp at fixed temperature T and pressure P is [2] ... 

The interactions between the polymer and ceramic phases of a composite are paramount if the material is to be used in any practical device. This is particularly important in 0-3 composites, where the polymer-filler interface within the system is considerable. Inadequate bonding between the components due to physical and chemical incompatibility, contaminants and defects on either surface can have profound effects on the ultimate integrity and performance of the composite. Careful selection of compatible components and the optimization of processing conditions are therefore of prime importance. 

Amphiphilic molecules [11-14] consist of mutually incompatible components. Since these components are chemically joined, complete segregation is impossible. It is replaced by various forms of microphase separation. These involve formation of segregated domains such that at least one of their dimensions is comparable to the molecular size. The domains are formed by spontaneous, thermodynamically driven aggregation of the amphiphiles. The process is thus often referred to as self-assembly. The resulting structures, micelles, lamellae, etc. can also form ordered mesophases. The microphase separation can take place in a solvent that selectively solubilizes one component or in a melt of neat amphiphiles. These characteristics are common to both polymeric and monomeric, low molecular weight amphiphiles. For the purposes of our discussion monomeric amphiphiles are defined, somewhat arbitrarily, as those consisting of 10 atoms. Polymeric amphiphiles, on the other hand, can incorporate 10 -10 atoms. The consequences of this difference are the topic of this article. 

The term amphiphile implies an affinity to two different media. Familiar amphiphilic molecules incorporate two incompatible components that give rise to this behavior. Similarly, in AB and ABA block copolymers there are two incompatible blocks of different solubility. However, ABC triblock copolymers incorporate three chemically different blocks. When the three blocks are mutually incompatible and of different solubilities the ABC surfactants can exhibit affinity to three different media rather than two. The consequences of this higher functionality have not been explored in detail. For example, little attention has been given to their behavior at interfaces. Linear ABC triblock copolymers or the corresponding star copolymers may be able to form two-dimensional mesophases [56], This can occur at the interface between two fluids I and II such that the B block is selectively solubilized in I while A and C are only soluble in II. In this situation, the A and C blocks are constrained to the surface and bound to each other. A two-dimensional amphiphile is obtained when the A and C blocks are incompatible. A dense monolayer of this type should undergo microphase separation leading to the formation of circular and striped mesophases. Note that cylindrical and lamellar mesophases are indistinguishable in this case. A mixed monolayer comprised of BC, BA, and ABC block copolymers will mimic the behavior of amphiphiles in the presence of two two-dimensional and incompatible fluids. When the ABC copolymers are a minority component, they should straddle the boundary line between the two-dimensional A and C phases. 

Hypergolic A hypergolic mixture ignites upon contact of the components without any external source of ignition (heat or flame). The only field, in which this is a desirable event, is in rocket fuel research. Accidental mixing of incompatible materials can lead to a fire or explosion. Here is one example provided by the staff at ILPI of what can happen, when incompatibles are mixed. Always read the labels on your bottles (don t assume a chemical s identity by the shape, size, or color of the bottle), and know what materials are incompatible with the chemicals that you are using. 

---